Pricing via Processing or Combating Junk Mail


%3 cluster_603bcc70_c827_439d_8f4d_7b3666512bcd Pricing via Processing or Combating Junk Mail _ea48ec1d_f9d4_4fb7_b39a_faa7b6e2ba95 Notes index _ea48ec1d_f9d4_4fb7_b39a_faa7b6e2ba95->__0:cluster_603bcc70_c827_439d_8f4d_7b3666512bcd _aa38f291_3f7a_4ba1_8ec2_b67da03e7833 Bitcoin is Worse is Better _aa38f291_3f7a_4ba1_8ec2_b67da03e7833->__1:cluster_603bcc70_c827_439d_8f4d_7b3666512bcd
We present a computational technique for combatting junk mail, in particular,
and controlling access to a shared resource, in general. The main idea is to
require a user to compute a moderately hard, but not intractable, function in
order to gain access to the resource, thus preventing frivolous use.

The pricing function may be chosen to have something like a _trap door_: given
some additional information the computation would be considerably less
expensive. We call this a /shortcut/. The shortcut may be used by the resource
manager to allocate cheap access to the resource, as the manager sees fit, by
bypassing the control mechanism.

For example, in the case of electronic mail the shortcut permits the post office to
grant bulk mailings at a price chosen by the post office, circumventing the cost of
directly evaluating the pricing function for each recipient.